/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */
package wx.xml.xalan.xpath.axes;

import wx.xml.xalan.xpath.Expression;
import wx.xml.xalan.xpath.ExpressionOwner;
import wx.xml.xalan.xpath.XPathVisitor;
import wx.xml.xalan.xpath.functions.FuncLast;
import wx.xml.xalan.xpath.functions.FuncPosition;
import wx.xml.xalan.xpath.functions.Function;
import wx.xml.xalan.xpath.objects.XNumber;
import wx.xml.xalan.xpath.operations.Div;
import wx.xml.xalan.xpath.operations.Minus;
import wx.xml.xalan.xpath.operations.Mod;
import wx.xml.xalan.xpath.operations.Mult;
import wx.xml.xalan.xpath.operations.Plus;
import wx.xml.xalan.xpath.operations.Quo;
import wx.xml.xalan.xpath.operations.Variable;

public class HasPositionalPredChecker extends XPathVisitor {
    private boolean m_hasPositionalPred = false;
    private int     m_predDepth         = 0;

    /**
     * Process the LocPathIterator to see if it contains variables
     * or functions that may make it context dependent.
     *
     * @param path LocPathIterator that is assumed to be absolute, but needs checking.
     * @return true if the path is confirmed to be absolute, false if it
     * may contain context dependencies.
     */
    public static boolean check(LocPathIterator path) {
        HasPositionalPredChecker hppc = new HasPositionalPredChecker();
        path.callVisitors(null, hppc);
        return hppc.m_hasPositionalPred;
    }

    /**
     * Visit a function.
     *
     * @param owner The owner of the expression, to which the expression can
     *              be reset if rewriting takes place.
     * @param func  The function reference object.
     * @return true if the sub expressions should be traversed.
     */
    public boolean visitFunction(ExpressionOwner owner, Function func) {
        if ((func instanceof FuncPosition) ||
            (func instanceof FuncLast))
            m_hasPositionalPred = true;
        return true;
    }

//	/**
//	 * Visit a variable reference.
//	 * @param owner The owner of the expression, to which the expression can 
//	 *              be reset if rewriting takes place.
//	 * @param var The variable reference object.
//	 * @return true if the sub expressions should be traversed.
//	 */
//	public boolean visitVariableRef(ExpressionOwner owner, Variable var)
//	{
//		m_hasPositionalPred = true;
//		return true;
//	}

    /**
     * Visit a predicate within a location path.  Note that there isn't a
     * proper unique component for predicates, and that the expression will
     * be called also for whatever type Expression is.
     *
     * @param owner The owner of the expression, to which the expression can
     *              be reset if rewriting takes place.
     * @param pred  The predicate object.
     * @return true if the sub expressions should be traversed.
     */
    public boolean visitPredicate(ExpressionOwner owner, Expression pred) {
        m_predDepth++;

        if (m_predDepth == 1) {
            if ((pred instanceof Variable) ||
                (pred instanceof XNumber) ||
                (pred instanceof Div) ||
                (pred instanceof Plus) ||
                (pred instanceof Minus) ||
                (pred instanceof Mod) ||
                (pred instanceof Quo) ||
                (pred instanceof Mult) ||
                (pred instanceof wx.xml.xalan.xpath.operations.Number) ||
                (pred instanceof Function))
                m_hasPositionalPred = true;
            else
                pred.callVisitors(owner, this);
        }

        m_predDepth--;

        // Don't go have the caller go any further down the subtree.
        return false;
    }


}

